A fresh "uncooked" corn tortilla is a flat thin circular cake, typically 6 inch in diameter, 1/16 inch thick and weight of about 1 ounce made of coarse corn meal and is commercially partially baked. In this state it is firm but pliable. Commonly, the corn tortilla is next cooked, deep-fried using a U-shaped mold to form a rigid, edible crispy taco shell wrapper. The molds, usually made of stainless steel and perforated to allow for the flow of oil and escape of water, include inner and outer U-shaped nesting components that hold the corn tortilla therebetween. In commercial units, an array of several molds is deep fried at approximately 350.degree. until most moisture is removed from the corn tortilla at which point the components are separated and the texture of the taco shell edible wrapper is crispy and rigidly fixed into the typical U-shape, which may be filled with various ingredients, e.g. cooked ground meat, grated cheese, chopped onions, shredded lettuce and diced tomatoes, with appropriate seasonings.
Taco shell cooking devices available for home purchase and use have imitated commercial deep fried method but on a smaller production scale. However, long cooking times, large quantities of expensive oil, and high energy requirements needed to maintain high temperatures and the inherent hazard of hot oil on a stove top have discouraged their widespread use. The inconvenience of home cooking can be avoided by purchasing packaged pre-cooked shells, but at a higher price. Further, many precooked shells are very brittle and require careful handling when filling and eating to prevent shattering.
In addition, avoiding excess animal and vegetable fats and oils is believed to be of great nutritional importance. The higher the initial moisture content of a deep fried material, the higher will be the oil absorption during frying.